A long-standing problem in the technology of lighting and light-source provision has been that of creating a light source having a wave length and wave pattern compatible with the physiology of the human eye. That is, the wave length of any light source should, ideally, fall within that range within which the eye can most easily focus. Further, the amplitude of such a light source should be as constant as possible, in order to conform with the characteristic of natural daylight (which exhibits an essentially constant amplitude).
More particularly, since the human eye has evolved in an environment of light which is predominantly in the yellow-green area of the spectrum (500 to 650 nanometers), the cones of the retina are thusly most sensitive to light within said range. There are, of course, three types of cones within the retina which respond to the following frequencies, e.g., 430 nanometers for purple; 535 nanometers for green; and 575 nanometers for orange. However, an ideal artificial light source should provide light having its greatest concentration of frequencies within the yellow-green area.
The above guidelines for an ideal artificial light source have, in the prior art, not been fully attained. More particularly, the prior art incandescent lamp, generally known as the Edison lamp, has differed from the ideal in at least three areas, namely, in that its emitted radiation contains a predominance of wave lengths in the red end of the spectrum within which the human eye does not focus properly, due to its inherent chromatic aberration; it exhibits an amplitude change of either 100 or 120 HZ; and, of course, there is the well-known energy-waste problem associated with such lamps.
The typical prior art discharge lamp, although more electrically efficient than the incandescent lamp, and, in the case of some lamps, emitting energy in the more desirable yellow-green region of the visual spectrum, nonetheless produces a high level periodic amplitude change of either 100 or 120 Hertz. It is to be appreciated that such a periodic amplitude change creates a "strobing" effect which, to many persons, results in the psychologically-disturbing subjective effect of objects appearing to jump from place to place, rather than appearing in smooth movement. Also, in said high level periodic amplitude situation, the eye and its associated feed-back mechanism is continually attempting to compensate for the changing brightness and to refocus due to the aforementioned strobing--the result of which is chronic (technically termed tonic) contraction of the meridional fibers of the iris, the sphincter muscles of the iris, and the ciliary muscles of the lens --all of which can result in burning sensations within the eye or headaches of several types or a combination of the above, according to the sensitivity of the particular individual. Accordingly, this continual re-adjusting of the light-admitting mechanism and the focusing mechanism results in greater eye fatigue than would occur in the absence of such a high level periodic amplitude change. Thusly, it is the primary objective of the present invention to provide an input circuit for discharge lamps which will not only alleviate the change of amplitude problem associated with prior art discharge lamps, but, at the same time, provide a substantial improvement in economy of operation.